Rotary pistons of the type having an encased, eccentrically positioned rotor with radially extending vanes which move in and out of the rotor, depending upon their position on the rotational cycle of the rotor, are used for example as pumps or turbines. One such device is described in U.S. Pat. No. 6,554,596 of Albert and David Patterson issued Apr. 29, 2003, in which the vane movement, in and out of the rotor, is achieved by cam surfaces within the casing which act on both inner and outer edges of the vanes.
In my co-pending U.S. patent application Ser. No. 10/680,236 entitled “Rotary Pistons”, the outward movement of the vanes of such a pump is achieved by upward extensions of shoulders at the sides of each vane, which upward extensions contain pins which are seated in races continuously extending in portions of the interior wall of the casing and positioned so that as the pins move about the races, they control the inward and outward movement of the vanes.
In my U.S. Pat. No. 6,896,502, issued May 24, 2005, an eccentrically positioned rotor is described and illustrated, provided with three planar vanes arranged in chord-like fashion in the rotor. The vanes' outward movement is accomplished by way of centrifugal force while inward movement of the vanes is caused by the cam action of the chamber walls bearing on outer edges of the vanes.
In my co-pending U.S. patent application Ser. No. 10/845,073, a positive displacement rotary piston pump is described and illustrated in which a pair of planar vanes are moveable in a slot diametrically extending through the rotor, the inward movement of the vanes being governed by cam action of the inner surface of the pump housing, and the outer movement being governed by centrifugal force and/or biasing.
It is an object of the present invention to provide an alternative constructions of positive displacement pump which will be adaptable to a wide range of different sizes and which will be adaptable to a wide variety of fluid and pressure conditions.